Flexible renal nerve ablation devices and related methods of use and manufacture

ABSTRACT

Medical devices for renal nerve ablation are disclosed. An example medical device for renal nerve ablation may include a catheter shaft having a distal region. The device may include an expandable member coupled to the distal region, a flexible circuit assembly coupled to the expandable member, and a pressure sensor disposed along the expandable member and positioned adjacent to the flexible circuit assembly. The flexible circuit assembly may include one or more pairs of bipolar electrodes and a temperature sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to U.S. Provisional Application Ser. No. 61/890,740, filed Oct. 14, 2013, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods for using and manufacturing medical devices. More particularly, the present disclosure pertains to medical devices and methods that relate to renal nerve ablation.

BACKGROUND

A wide variety of intracorporeal medical devices have been developed for medical use, for example, intravascular use. Some of these devices include guidewires, catheters, and the like. These devices are manufactured by any one of a variety of different manufacturing methods and may be used according to any one of a variety of methods. Of the known medical devices and methods, each has certain advantages and disadvantages. There is an ongoing need to provide alternative medical devices as well as alternative methods for manufacturing and using medical devices.

SUMMARY

Medical devices and methods for making and using medical devices are disclosed herein. One such exemplary medical device may include a renal nerve ablation device that has a catheter shaft with a distal region. In addition, the device may include an expandable member coupled to the distal region. The device may further include a flexible circuit assembly coupled to the expandable member, such that the flexible circuit assembly may include one or more pairs of bipolar electrodes and a temperature sensor. The device may further include a pressure sensor disposed along the expandable member and positioned adjacent to the flexible circuit assembly.

Another exemplary medical device for renal nerve ablation may include a catheter shaft having a distal region. A compliant balloon may be coupled to the distal region of the catheter shaft. One or more pairs of bipolar electrodes may be coupled to the compliant balloon. Further, the device may include one or more temperature sensors and one or more pressure sensors that are each coupled to the compliant balloon.

An exemplary method for ablating renal nerves may include providing a renal nerve ablation device that includes a catheter shaft having a distal region. The device may further include a compliant balloon coupled to the distal region, and one or more pairs of bipolar electrodes coupled to the compliant balloon. Further, the device may include one or more temperature and pressure sensors that are each coupled to the compliant balloon. The method may also include advancing the renal nerve ablation device through a blood vessel to a position within a renal artery. Further, the method may include expanding the compliant balloon, which may be followed by sensing contact between the compliant balloon and the renal artery with the one or more pressure sensors. Still further, the method may include activating at least one of the one or more pairs of bipolar electrodes.

The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures, and Detailed Description, which follow, more particularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the present disclosure and together with the description, serve to explain the principles of the disclosure.

FIG. 1 is a schematic view illustrating an exemplary renal nerve ablation system, according to some embodiments of the present disclosure.

FIG. 2 illustrates a related art renal nerve ablation device within a vessel.

FIG. 3 illustrates an exemplary renal nerve ablation device, in accordance with the present disclosure.

FIG. 4 illustrates another exemplary renal nerve ablation device, in accordance with the present disclosure.

DETAILED DESCRIPTION

The following description should be read with reference to the drawings, which are not necessarily to scale, wherein like reference numerals indicate like elements throughout the several views. The detailed description and drawings are intended to illustrate but not limit the claimed invention. Those skilled in the art will recognize that the various elements described and/or shown may be arranged in various combinations and configurations without departing from the scope of the disclosure. The detailed description and drawings illustrate example embodiments of the claimed invention.

For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.

All numeric values are herein assumed to be modified by the term “about,” whether or not explicitly indicated. The term “about”, in the context of numeric values, generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the term “about” may include numbers that are rounded to the nearest significant figure. Other uses of the term “about” (i.e., in a context other than numeric values) may be assumed to have their ordinary and customary definition(s), as understood from and consistent with the context of the specification, unless otherwise specified. The recitation of numerical ranges by endpoints includes all numbers within that range, including the endpoints (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. It is noted that references in the specification to “an embodiment”, “some embodiments”, “other embodiments”, etc., indicate that the embodiment(s) described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it would be within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described, unless clearly stated to the contrary. That is, the various individual elements described below, even if not explicitly shown in a particular combination, are nevertheless contemplated as being combinable or arrangable with each other to form other additional embodiments or to complement and/or enrich the described embodiment(s), as would be understood by one of ordinary skill in the art.

Certain treatments are aimed at the temporary or permanent interruption or modification of select nerve function. In some embodiments, the nerves may be sympathetic nerves. One example treatment is renal nerve ablation, which is sometimes used to treat conditions such as or related to hypertension, congestive heart failure, diabetes, or other conditions impacted by high blood pressure or salt retention. The kidneys produce a sympathetic response, which may increase the undesired retention of water and/or sodium. The result of the sympathetic response, for example, may be an increase in blood pressure. Ablating some or all of the nerves running to the kidneys (e.g., disposed adjacent to or otherwise along the renal arteries) may reduce or eliminate this sympathetic response, which may provide a corresponding reduction in the associated undesired symptoms (e.g., a reduction in blood pressure).

Some embodiments of the present disclosure relate to a power generating and control apparatus, often for the treatment of targeted tissue in order to achieve a therapeutic effect. In some embodiments, the target tissue is tissue containing or proximate to nerves. In other embodiments, the target tissue is sympathetic nerves, including, for example, sympathetic nerves disposed adjacent to blood vessels. In still other embodiments the target tissue is luminal tissue, which may further comprise diseased tissue such as that found in arterial disease.

In some embodiments of the present disclosure, the ability to deliver energy in a targeted dosage may be used for nerve tissue in order to achieve beneficial biologic responses. For example, chronic pain, urologic dysfunction, hypertension, and a wide variety of other persistent conditions are known to be affected through the operation of nervous tissue. For example, it is known that chronic hypertension that may not be responsive to medication may be improved or eliminated by disabling excessive nerve activity proximate to the renal arteries. It is also known that nervous tissue does not naturally possess regenerative characteristics. Therefore it may be possible to beneficially affect excessive nerve activity by disrupting the conductive pathway of the nervous tissue. When disrupting nerve conductive pathways, it is particularly advantageous to avoid damage to neighboring nerves or organ tissue. The ability to direct and control energy dosage is well-suited to the treatment of nerve tissue. Whether in a heating or ablating energy dosage, the precise control of energy delivery as described and disclosed herein may be directed to the nerve tissue. Moreover, directed application of energy may suffice to target a nerve without the need to be in exact contact, as would be required when using a typical ablation probe. For example, eccentric heating may be applied at a temperature high enough to denature nerve tissue without causing ablation and without requiring the piercing of luminal tissue. However, it may also be desirable to configure the energy delivery surface of the present disclosure to pierce tissue and deliver ablating energy similar to an ablation probe with the exact energy dosage being controlled by a power control and generation apparatus.

In some embodiments, efficacy of the denervation treatment can be assessed by measurement before, during, and/or after the treatment to tailor one or more parameters of the treatment to the particular patient or to identify the need for additional treatments. For instance, a denervation system may include functionality for assessing whether a treatment has caused or is causing a reduction in neural activity in a target or proximate tissue, which may provide feedback for adjusting parameters of the treatment or indicate the necessity for additional treatments.

Many of the devices and methods described herein are discussed relative to renal nerve ablation and/or modulation. However, it is contemplated that the devices and methods may be used in other treatment locations and/or applications where sympathetic nerve modulation and/or other tissue modulation including heating, activation, blocking, disrupting, or ablation are desired, such as, but not limited to: blood vessels, urinary vessels, or in other tissues via trocar and cannula access. For example, the devices and methods described herein can be applied to hyperplastic tissue ablation, cardiac ablation, pain management, pulmonary vein isolation, pulmonary vein ablation, tumor ablation, benign prostatic hyperplasia therapy, nerve excitation or blocking or ablation, varicose veins, modulation of muscle activity, hyperthermia or other warming of tissues, etc. The disclosed methods and apparatus can be applied to any relevant medical procedure, involving both human and non-human subjects. The term modulation refers to ablation and other techniques that may alter the function of affected nerves and other tissue.

FIG. 1 is a schematic view of an illustrative renal nerve ablation system 10 in situ.

In the illustrated embodiment, the system 10 is used to ablate one or more renal nerves of a right kidney K. In the illustrated embodiment, only the right kidney K is shown for purposes of simplicity, however, the system 10 can be used for both right and left kidneys, and associated renal vasculature, such as the renal artery RA that branches laterally from the abdominal aorta A.

In general, system 10 may include one or more conductive element(s) 18 providing power to renal ablation system 12 disposed within a sheath 14, which is shown in more detail in subsequent figures. Although not shown, a proximal end of conductive element 18 may be connected to a control and power element(s) 16, which supplies the necessary electrical energy to activate one or more electrodes disposed at or near a distal end of the renal ablation system 10. The system 10 may further include connectors 20, 22 to electrically connect the conductive element(s) 18 to the control and power element 16. The connector 20 may be designed so as to conform to the connector 22. For example, the connector 20 may be a male connector including a pin, whereas the connector 22 may be a female connector with a hole to receive that pin. Other variations may also be contemplated. A connective link 24 such as a wire may connect the connector 22 to the control and power element 16. The control and power element 16 may include monitoring elements to monitor parameters, such as power, temperature, voltage, pulse size and/or shape and other suitable parameters as well as suitable controls for performing the desired procedure. The control and power element 16 may control a radio frequency (RF) electrode. It is contemplated that any desired frequency in the RF range may be used, for example, from 450-500 kHz. It is, however, contemplated that different types of energy outside the RF spectrum may be used as desired, for example, but not limited to, ultrasound, microwave, and laser technologies.

FIG. 2 illustrates a portion of an example renal nerve ablation device 200 disposed within a lumen 206 of a vessel 204. In particular, the device 200 includes a catheter shaft 202 having an expandable member 210 attached to a distal region 208 of the catheter shaft 202. In the illustrated embodiment, the expandable member 210 is a non-compliant balloon. The device 200 further includes two electrode assemblies 212 a and 212 b disposed on an external surface of the non-compliant balloon 210.

Some blood vessels may have a generally tapered or narrowing shape. Because of this, during a medical procedure portions of the non-compliant balloon 210 may contact the vessel wall, while other portions, particularly, proximal portions, may be spaced from the vessel wall, thereby leading to mal-apposition of the non-compliant balloon 210 at the proximal portion. In the areas, where the portions of the non-compliant balloon 210 is in contact (e.g., narrowed areas), there may be more expansion force on the vessel wall and this may sometimes deform the vessel, thus, leading to stress induced trauma to the vessel 204. In view of the above, the present disclosure discloses renal ablation devices 300, 400, which will be discussed below in detail.

FIG. 3 illustrates an exemplary renal nerve ablation device 300. The renal nerve ablation device 300 may include a catheter shaft 302 having its distal region attached to an expandable member, such as a balloon 304. In the illustrated embodiment, the balloon 304 may be a compliant balloon. Although not shown, a proximal region of the catheter shaft 302 may extend proximally to remain outside of the patient's body. The catheter shaft 302 may also include one or more lumens extending between the proximal and distal regions, where the catheter shaft 302 may be adapted to enter a patient's body. Specifically, the distal region of the catheter shaft 302 may be advanced within the patient's body to reach a target site. In certain instances, the proximal region of the catheter shaft 302 may include a hub attached thereto for connecting to other diagnostic and/or treatment devices, which provides a port for facilitating other interventions.

As shown, the catheter shaft 302 may be a tubular structure defining a circular cross-section. Those skilled in the art will appreciate that other suitable cross-sections, such as rectangular, polygonal, irregular, etc., may also be contemplated. In addition, the cross-section of the catheter shaft 302 may be uniform along its length or may vary.

Materials employed to manufacture the compliant balloon 304 may include any suitable biocompatible and compliant materials, such as, but are not limited to, polymers such as low durometer Pebax, polyether block amide, polyurethane, silicone or the like. In at least some embodiments, the balloon material may match with material of electrodes pad 312 (discussed below). In some embodiments, the thickness of the electrodes pad 312 may be same or less than that of the compliant balloon 304. In above embodiments, the material employed may have an insulating property, which may electrically isolate the catheter shaft 302 relative to the compliant balloon 304 and/or to the bodily fluid. Materials employed to manufacture catheter shaft 302 may include polymers. Some examples of suitable polymers may include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, for example, DELRIN® available from DuPont), polyether block ester, polyurethane (for example, Polyurethane 85A), polypropylene (PP), polyvinylchloride (PVC), polyether-ester (for example, ARNITEL® available from DSM Engineering Plastics), ether or ester based copolymers (for example, butylene/poly(alkylene ether) phthalate and/or other polyester elastomers such as HYTREL® available from DuPont), polyamide (for example, DURETHAN® available from Bayer or CRISTAMID® available from Elf Atochem), elastomeric polyamides, block polyamide/ethers, polyether block amide (PEBA, for example available under the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA), silicones, polyethylene (PE), Marlex high-density polyethylene, Marlex low-density polyethylene, linear low density polyethylene (for example REXELL®), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polytrimethylene terephthalate, polyethylene naphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), poly paraphenylene terephthalamide (for example, KEVLAR®), polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMS American Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC), poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS 50A), polycarbonates, ionomers, biocompatible polymers, other suitable materials, or mixtures, combinations, copolymers thereof.

Further, the device 300 may include a flexible circuit assembly 306 coupled to the compliant balloon 304. Flexible circuit assembly 306 may include a semi- or compliant material such a PET/PEN with a printed conductive circuit (e.g., a metallic ink or carbon-based materials, such as carbon nanotubes, graphene or nanobuds), whereby the conductive pathways are printed in a slightly meandering pattern allowing the circuit pathways to be stretched. In some cases, the flexible circuit assembly 306 may be adhesively connected to the outer surface of compliant balloon 304. In particular, the flexible circuit assembly 306 may be coupled to external surface of the compliant balloon 304, such that inflation of the compliant balloon 304 may stretch the flexible circuit 306 to conform to a vessel.

The flexible circuit 306 may include one or more pairs of bipolar electrodes, such as bipolar electrode pairs 312 a and 312 d, 312 b and 312 e, and 312 c and 312 f and in some embodiments, the electrode pairs 312 a and 312 d, 312 b and 312 e, and 312 c and 312 f may be printed on the compliant balloon 304. In some embodiments, the conductive pathways may be directly printed on the compliant balloon surface, while a small electrode assembly is adhesively bonded to the balloon surface. The printed conductive pathways can be printed after assembling of the electrode pads to the balloon surface, such they might run over the balloon surface as well as the electrode pads. This will allow for relatively smaller electrode pads. Although three pairs of bipolar electrodes are shown, but any suitable number of bipolar electrode pairs may be employed, such as one, two, four, etc.

In general, the electrodes (312 a-312 f) may be printed on the flexible circuit assembly 306. For example, the flexible circuit 306/bipolar electrodes 312 can be printed via inkjet and screen printing methods. In some cases, the flexible circuit 306 may partially be printed electrodes on the compliant balloon 304 (e.g., flexible, printed electrode assemblies).

Further, the flexible circuit 306 may include a set of thermistors 314 a and 314 b configured to measure the temperature at the electrodes site. The thermistors 314 a and 314 b may be employed to measure, or monitor, the temperature of the vessel wall, such as in real-time (i.e., during the renal ablation procedure, thus providing acute physician feedback). If the temperature crosses a set threshold, feedback may be provided to the control and power element 16, which may automatically reduce the power into the electrodes, as such avoiding a further rise or causing a reduction of the temperature, in order to reduce or avoid incidence of vessel trauma due to over-heating. For example, the control and power element 16 may decrease the amount of ablation energy, if the temperature is too high. In another example, the control and power element 16 may increase the ablation energy, if the temperature becomes too low. In addition, the thermistors 314 a and 314 b may measure the temperature at the electrodes (312 a to 312 f).

The compliant balloon assembly may further include a set of pressure sensors 310 a and 310 b disposed along the compliant balloon 304, such as at locations at or adjacent to the flexible circuit 306. The pressure sensors 310 a and 310 b may be configured to sense contact between an outer surface of the compliant balloon 304 and a target tissue (e.g., via sensing increased resistance to further inflation). The sensed pressure may facilitate the operator in regulating inflation pressure of the compliant balloon 304, and thus the apposition of the flexible circuit 306. To this end, a controlled pressure may reduce or avoid an over-expansion of a vessel due to excessive applied pressure, thereby reducing or avoiding stress induced trauma to the vessel (as shown in FIG. 2).

In some embodiments, the device 300 may incorporate pressure-sensor feedback mechanism for the operator to control inflation of the compliant balloon 304, enhancing the operator's ability to inflate the balloon to a pressure in order to achieve the appropriate contact with the vessel wall. For example, the pressure sensors 310 a, 310 b may provide real-time, acute feedback to the operator to stop or reduce the inflation if the pressure is too high. In another example, the pressure sensors 310 a, 310 b may also provide feedback in case that a portion of the compliant balloon 304 is not in contact with the vessel wall.

In some embodiments, the device 300 may incorporate pressure-sensor feedback mechanism to be send to controller unit 16, which allows the controller unit 16 to automatically adjust the power level, pulse size and shape to each electrode pair based on one or more of the following parameters: power level, temperature, pressure, and total ablation time.

In yet another embodiment, controller unit 16 may be designed to automatically adjust, reduce, or increase the pressure level within the balloon to maintain adequate wall contact during the procedure.

In the illustrated embodiment, the pressure sensor 310 a may be disposed adjacent the proximal end region of the compliant balloon 304, whereas the pressure sensor 310 b may be disposed adjacent to a distal end region of the compliant balloon 304. In some embodiments, the device 300 may include at least proximal pressure sensor such as pressure sensor 310 a to sense whether the proximal part of the compliant balloon 304 is in contact with the vessel wall. Such an arrangement of the pressure sensors (310 a and 310 b) may facilitate real-time, acute measurement of the pressure over a wide length of the compliant balloon 304, and thus the vessel, thereby enhancing accuracy of the procedure. This arrangement may also be useful when medical device 300 is utilized in a tapered blood vessel because, for example, the proximal pressure sensor 310 a can help to determine whether or not proximal portions of the compliant balloon 304 are in contact with the blood vessel wall. It should be noted that any suitable number of pressure sensors including one, three, four, etc., may be disposed in any suitable arrangement along the flexible circuit 306, as desired.

Disposing the pressure sensor 310 a at or near the proximal end of the compliant balloon 304 may also allow medical device 300 to have only a single temperature sensor (e.g., one of the thermistors 314 a, 314 b). This may be because, for example, the compliant balloon 304 may conform with substantially equal pressure along the vessel wall, such that measuring the contact pressure at just one point, will provide knowledge about the conformability of the entire balloon surface.

The pressure sensors 310 a and 310 b may be any suitable sensor, such as a polyethylene terephthalate foil pressure sensor. Other pressure sensors are contemplated.

Although a single flexible circuit 306 is shown, it should be noted that any suitable number of flexible circuits may be employed including two, three, four, etc. Further, one or more flexible circuits 306 may be positioned in any suitable arrangement along the external surface of the compliant balloon 304. In general, the flexible circuit(s) 306 can be arranged along the external surface of the compliant balloon 304 to attain desired lesion pattern(s). Exemplary lesion patterns, and thus the arrangement of the flexible circuits 306, may be helical along the longitudinal length of the compliant balloon 304.

FIG. 4 illustrates another exemplary renal nerve ablation device 400. The device 400 may include a catheter shaft 402 having an expandable member 404 attached to its distal region. The expandable member 404 may include a compliant balloon having a structure and function similar to that of the compliant balloon 304 of FIG. 3. Similarly, the catheter shaft 402 also has a structure and function similar to that of the catheter shaft 302 of FIG. 3.

The device 400 may further include a flexible circuit assembly 406 coupled to an external surface of the compliant balloon 404. In some cases, the flexible circuit assembly 406 may be adhesively or mechanically coupled on the compliant balloon 404. The flexible circuit 406 may include one or more electrode pads, each having one or more pairs of bipolar electrodes. For example, a first electrode pad may include three bipolar electrode pairs 412 a and 412 d, 412 b and 412 e, and 412 c and 412 f (collectively 412). Similarly, a second electrode pad, which may be separated to the first electrode pad by a distance, may include another three bipolar electrode pairs 416 a and 416 d, 416 b and 416 e, and 416 c and 416 f (collectively 416). In some embodiments, these electrode pairs 412, 416 may be printed on the compliant balloon 404. Although each of these electrode pads includes three pairs of bipolar electrodes, but any suitable number of bipolar electrode pairs may be employed, such as one, two, four, etc.

In general, the electrode pairs 412, 416 may be printed on the flexible circuit 406 using known, related art, or later developed printing methods, including, but not limited to, inkjet and screen printing methods. In some embodiments, the flexible circuit 406 may be thin film pads.

Further, the flexible circuit 406 may include three thermistors 414 a, 414 b, and 414 c configured to measure the temperature at the electrodes site. In particular, thermistor 414 a may be placed adjacent the first electrode pad, thermistor 414 c may be placed adjacent the second electrode pad, and thermistor 414 b may be placed in between the first and second electrode pad. Each thermistor (414 a, 414 b, and 414 c; collectively 414) may be employed to measure the temperature of the vessel wall, such as in real-time (i.e., during the renal ablation procedure). If the temperature crosses a set threshold, feedback may be provided to the control and power element 16, which may automatically change the temperature. This temperature control may reduce or avoid incidence of vessel trauma due to over-heating. In addition, the thermistors 414 may measure the temperature of flexible circuit 406, which may reduce or avoid fouling of electrodes during the ablation procedure.

The flexible circuit 406 may further include a set of pressure sensors 410 a and 410 b (collectively 410) disposed along the compliant balloon 404, while positioned at or adjacent to the flexible circuit 406. The pressure sensors 410 a and 410 b may be configured to sense contact between an outer surface of the compliant balloon 404 and a target tissue. The sensed pressure may facilitate the operator in regulating the inflation of the compliant balloon 404, and thus the apposition of the flexible circuit 406. To this end, a controlled pressure may reduce or avoid an over-expansion of a vessel due to excessive applied pressure, thereby reducing or avoiding stress induced trauma to the vessel (as shown in FIG. 2)

Similar to the above embodiments, the two pressure sensors 410 a and 410 b may be disposed at or adjacent the proximal and distal end regions of the compliant balloon 404, respectively. In some embodiments, the device 400 may include at least proximal pressure sensor such as pressure sensor 410 a to sense whether the proximal part of the compliant balloon 404 is in contact with the vessel wall. Such an arrangement of the pressure sensors 410 may facilitate real-time, acute measurement of the pressure over a wide length of the compliant balloon 404, and thus the vessel, thereby enhancing accuracy of the procedure. It should be noted that any suitable number of pressure sensors, including one, three, four, etc., may be disposed in any suitable arrangement along the flexible circuit 406, as desired.

In some embodiments, the device 400 may incorporate pressure-sensor feedback mechanism for the operator to control inflation of the compliant balloon 404, enhancing the operator's ability to inflate the compliant balloon 404 to a pressure in order to achieve the appropriate contact with the vessel wall. For example, the pressure sensors 410 a, 410 b may provide real-time, acute feedback to the operator to stop or reduce the inflation if the pressure is too high. In another example, the pressure sensors 410 a, 410 b may also provide feedback in case the compliant balloon 404, or a portion thereof, is not in contact with the vessel wall.

The pressure sensors 410 a and 410 b may be any suitable sensor, such as a polyethylene terephthalate foil pressure sensor. Other suitable known, related art, or later developed pressure sensors may also be employed, without departing from the scope and spirit of the present disclosure.

In some embodiments, the flexible circuit 406 may be helically disposed about the longitudinal axis of the catheter shaft 402. The flexible circuit 406 shown may be disposed at an angle relative to the longitudinal axis of the catheter shaft 402. Angling the flexible circuit 406 may help withdrawing the catheter shaft 402 into a guide catheter.

An exemplary method of ablating renal nerves can utilize either device 300 or 400 (as shown in FIGS. 3-4, respectively). The device 300 may be advanced through a blood vessel to a position within a renal artery. Subsequently, an operator may inflate the device 300 to expand the compliant balloon (i.e., the expandable balloon 304 of FIG. 3). In the expanded position, the electrodes may come into contact with the vessel, and the pressure between the compliant balloon and the renal artery can be sensed using the pressure sensor 410 a, for example. Once a desired pressure is attained, one or more pairs of bipolar electrodes may be activated to ablate the surrounding renal nerves and/or tissue.

Although the embodiments described above have been set out in connection with a renal nerve ablation device, those of skill in the art will understand that the principles set out there can be applied to any device where it is deemed advantageous to provide flexibility to the renal nerve ablation device. Conversely, constructional details, including manufacturing techniques and materials, are well within the understanding of those of skill in the art and have not been set out in any detail here. These and other modifications and variations are well within the scope of the present disclosure and can be envisioned and implemented by those of skill in the art.

Other embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein. It is intended that the specification and examples be considered as exemplary only, and departure in form and detail may be made without departing from the scope and spirit of the present disclosure as described in the following claims. 

What is claimed is:
 1. A medical device for renal nerve ablation, comprising: a catheter shaft having a distal region; an expandable member coupled to the distal region; a flexible circuit assembly coupled to the expandable member, the flexible circuit assembly including one or more pairs of bipolar electrodes and a temperature sensor; and a pressure sensor disposed along the expandable member and positioned adjacent to the flexible circuit assembly.
 2. The medical device of claim 1, wherein the expandable member includes a compliant balloon.
 3. The medical device of claim 2, wherein the compliant balloon includes polyether block amide.
 4. The medical device of claim 2, wherein the compliant balloon includes polyurethane.
 5. The medical device of claim 1, wherein the flexible circuit assembly includes one or more additional temperature sensors.
 6. The medical device of claim 1, wherein the pressure sensor is capable of sensing contact between an outer surface of the expandable member and a target tissue.
 7. The medical device of claim 1, further comprising one or more additional pressure sensors.
 8. The medical device of claim 1, wherein the catheter shaft has a longitudinal axis and wherein at least a portion of the flexible circuit assembly is disposed at an angle relative to the longitudinal axis.
 9. The medical device of claim 1, wherein the catheter shaft has a longitudinal axis and wherein at least a portion of the flexible circuit assembly is helically disposed about the longitudinal axis.
 10. The medical device of claim 1, wherein the flexible circuit assembly includes one or more printed electrode pads.
 11. The medical device of claim 1, wherein the pressure sensor includes a polyethylene terephthalate foil pressure sensor.
 12. The medical device of claim 1, wherein the flexible circuit assembly includes one pair of bipolar electrodes.
 13. The medical device of claim 1, wherein the flexible circuit assembly includes two or more pairs of bipolar electrodes.
 14. A medical device for renal nerve ablation, comprising: a catheter shaft having a distal region; a compliant balloon coupled to the distal region; one or more pairs of bipolar electrodes coupled to the compliant balloon; one or more temperature sensors coupled to the compliant balloon; and one or more pressure sensors coupled to the compliant balloon.
 15. The medical device of claim 14, wherein two or more pairs of bipolar electrodes are coupled to the compliant balloon.
 16. The medical device of claim 14, wherein the one or more pairs of bipolar electrodes are disposed along a flexible circuit coupled to the compliant balloon.
 17. The medical device of claim 16, wherein the catheter shaft has a longitudinal axis and wherein at least a portion of the flexible circuit is disposed at an angle relative to the longitudinal axis.
 18. The medical device of claim 16, wherein the catheter shaft has a longitudinal axis and wherein at least a portion of the flexible circuit is helically disposed about the longitudinal axis.
 19. The medical device of claim 14, wherein at least one of the one or more pressure sensors is disposed adjacent to a proximal end region of the compliant balloon.
 20. A method for ablating renal nerves, the method comprising: providing a renal nerve ablation device, the renal nerve ablation device comprising: a catheter shaft having a distal region, a compliant balloon coupled to the distal region, one or more pairs of bipolar electrodes coupled to the compliant balloon, one or more temperature sensors coupled to the compliant balloon, and one or more pressure sensors coupled to the compliant balloon; advancing the renal nerve ablation device through a blood vessel to a position within a renal artery; expanding the compliant balloon; sensing contact between the compliant balloon and the renal artery with the one or more pressure sensors; and activating at least one of the one or more pairs of bipolar electrodes. 